/Engine/Source/Editor/PropertyEditor/Public/DetailLayoutBuilder.h
If this is a sub-object customization it will return those sub objects. Otherwise the root objects will be returned.
void GetObjectsBeingCustomized ( [TArray](API\Runtime\Core\Containers\TArray)< [TWeakObjectPtr](API\Runtime\Core\UObject\TWeakObjectPtr)< [UObject](API\Runtime\CoreUObject\UObject\UObject) > > & OutObjects ) const